This invention relates generally to disk drive types of mass data storage systems, and, more particularly, to circuits interfacing with read and write heads of such systems.
A disk drive storage system includes one or more rotating disks having magnetizable material coated on its surfaces. A read/write head is associated with each surface, all of the heads being moved together radially across the rotating disk surfaces to reach addressed data recording tracks. The most common type read/write head uses a single inductive element for both writing data onto the disk surface and reading data from it.
Currently, a different type of read/write head is being used to a limited extent and being contemplated for large scale use by disk drive manufacturers. This head includes separate read and write elements. The read element is a magneto-resistive type; that is, its resistance changes as a function of the magnetic field it which it is placed, and itself is non-magnetic. The write element is a magnetic thin film type. Movement toward use of this type of head is occurring because of its ability to read and write data at significantly higher densities on magnetic disk surfaces than possible with the popular single element head.
Circuits for interfacing with single element heads of the conventional type connect both a preamplifier read channel and a write driver through a common multiplexer (switch) that selects one of the heads at a time for connection with a disk controller. Since this is not suitable for the newer two-element heads, it is a primary object of the present invention to provide appropriate interface circuitry that allows the advantages of the newer heads to be fully utilized.